Bearing wear is
affected by many factors. For the most part, tests conducted by Transport
Dynamics subject journal bearings to 20,000 psi loads with the bearing
fixed and the shaft oscillating. The values shown in the charts on page
6 are representative of the normal wear rate range that can be expected
when amplitude is ±45°, frequency is 10 CPM, and shaft finish is 16
RMS under room temperature conditions.
It will be noted
that a wear-in period takes place during the first few thousand cycles.
During this period some PTFE is transferred to the mating surface. In
addition, the fibers are generally reoriented, the high points of the
weave are flattened and adjacent fibers tend to blend together. After
the break-in period, the bearing surface will become smooth and shiny.
Because of the many
variables which influence wear, it is extremely difficult to project
bearing life for all types of applications. For this reason, the Transport
Dynamics Engineering Department should be consulted when questions of
this nature arise. Wear life calculations are based on rubbing distance